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Chapter 10: Chemical Reactions

Chapter 10: Chemical Reactions

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Chapter 10: Chemical Reactions

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  1. Chapter 10: Chemical Reactions

  2. Chemical Reactions • Defn – process by which the atoms of one or more substances are rearranged - new substances are formed

  3. Evidences of a chemical reaction 1) gas production 2) light production 3) temperature change (endo/exothermic) 4) precipitate formed (solid from 2 liquids) 5) permanent color change

  4. Energy is stored in compounds as chemical potential energy due to specific arrangements of atoms. A chemical reaction changes the potential energy present. When energy is lost as heat, it is called a __________________. These reactions get hotter. Sometimes energy is gained; heat is added for a reaction to occur. These are called ______________________, which get colder. exothermic reaction endothermic reaction

  5. Word Equation • Defn – equation expressed in words Iron + chlorine  iron (III) chloride

  6. Formula Equation • Defn – equation with chemical formulas • Coefficients – whole # placed in front of compound • Balances the number of atoms 2 Fe + 3 Cl2 2 FeCl3

  7. Parts Of A Reaction • Symbols heat added (s) solid Δ (l) liquid (g) gas (aq) aqueous (dissolved in water)

  8. example • Solid calcium carbonate reacts with a solution of hydrochloric acid to produce aqueous calcium chloride, gaseous carbon dioxide, and liquid water + HCl (aq) CaCO3 (s) CaCl2 (aq) + CO2 (g) + H2O (l)

  9. Diatomic Elements • Defn – 7 elements that NEVER occur as singular atoms (always paired with an the same or different element) H2 O2 F2 Br2 I2 N2 Cl2 Ex: 2 HCl + K  2 KCl + H2

  10. Balancing Equations • Number of reactant atoms on left of an element must equal number of product atoms on the right • Must obey law of conservation of mass

  11. Rules for balancing equations 1) Only coefficientsare changed in balancing reactions 2) Never change subscript during balancing 3) Coefficients are placed in front of compound and multiplied across compound to get total # of atoms of each element

  12. Helpful Hints • Balance hydrogen and oxygen last • Balance polyatomic ions as a group if present on both reactants and products

  13. Before After MgCl2 + NaOH  Mg(OH)2 + NaCl 1 Mg 1 Na 1 Mg 1 Na 2 Cl 1 OH 1 Cl 2 OH MgCl2 + 2 NaOH  Mg(OH)2 + 2 NaCl 1 Mg 2 Na 1 Mg 2 Na 2 Cl 2 (OH) 2 Cl 2 (OH)

  14. Sample Problems • sodium and chlorine combine to form sodium chloride 2 + 1 Cl2  2 NaCl Na

  15. Sample Problems • sodium hydroxide and calcium bromide react to produce calcium hydroxide and sodium bromide 2 1 NaOH + CaBr2  1 Ca(OH)2 + 2 NaBr

  16. Sample Problems • aluminum sulfate and calcium hydroxide produce calcium sulfate and aluminum hydroxide 1 3 Al2(SO4)3 + Ca(OH)2  3 2 CaSO4 + Al(OH)3

  17. Classifying Chemical Reactions • Synthesis • Decomposition • Single replacement • Double Replacement • Combustion

  18. Synthesis • Defn – two or more substances react to form ONE product A + B  AB

  19. Hey baby let’s get jiggy.

  20. Synthesis • reaction of two elements 2 3 2 ___Al + ___Cl2 ___AlCl3 Al3+ Cl1-

  21. Decomposition • defn – one substance breaks down into two or more simpler products AB  A + B

  22. Break yoself fool!

  23. Decomposition • Ex reaction 2 2 3 __ NaN3 (s)  ___ Na (s) + ___ N2 (g) 2 2 1 __ CaO (s)  ___ Ca (s) + ___ O2 (g)

  24. Single Replacement Reactions • Defn – one element replaces another element in a compound to form new compound A + BX  AX + B

  25. I’m gon’ dance with yo’ lady

  26. Reactivity Series • metals • halogens Li K Ca Na Mg Al Mn Zn Fe Ni Sn Pb Cu Ag Au most active least active F Cl Br I most active least active

  27. examples • aluminum + iron (III) oxide Fe3+ O2- Stronger? 2 1 2 1 + Al + Fe2O3 Fe Al2O3 Al3+ O2-

  28. examples • silver + copper (I) nitrate Cu1+ NO31- Stronger? Ag + CuNO3 NO RXN

  29. examples • fluorine gas + sodium bromide Stronger? 1 2 2 1 F2 + NaBr NaF + Br2 Na1+ F1-

  30. examples • chlorine gas + hydrogen fluoride Stronger? Cl2 + HF NO RXN

  31. Double Replacement • Defn – exchange of cations between two ionic compounds A B + C D  AD + CB switch

  32. 3 possible products of double replacement rxns • Precipitate • Gas • Water

  33. Ex problem • lithium iodide and aqueous silver nitrate react Li1+ I1- Ag1+ NO31- Li I Ag I (s) + AgNO3 LiNO3 +

  34. Combustion • defn – compound reacts with O2 • Hydrocarbon – cmpd w/ only carbon and hydrogen

  35. Combustion • Combustion of hydrocarbons ALWAYS produces CO2 and H2O CxHy + O2 CO2 + H2O

  36. Ex problem • show combustion of propane (C3H8) gas 1 C3H8 + 5 O2 3 CO2 + 4 H2O